Gravity Modeling, Seismic Stratigraphy, and Thermal Maturity Modeling of Hydrocarbons of the Permian Foreland Basin, USA, and the Sergipe-Alagoas Rifted-Passive Margin, Brazil



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The Permian Basin in West Texas is by far the most prolific oil-producing onshore basin in the U.S., and the Sergipe-Alagoas Basin is the sixth-largest hydrocarbon-producing basin in Brazil. The purpose of this dissertation is to better understand the changing tectonic setting, crustal structure, and sedimentary basin fill influenced the hydrocarbon potential of these two basins. In Chapter 2, I created 2D and 3D gravity models to better define the tectonic origin of the Abilene gravity minimum (AGM) underlying the northern Permian Basin. I inferred the AGM as a Precambrian rift zone composed of lower density granitic and metasedimentary rocks. Basement structure defines the limits of deep basinal areas that may host productive, thermally mature source rock kitchens controlled in part by strike-slip faults aligned with AGM edges. In Chapter 3, I created a 3D full tensor gradiometry (FTG) gravity model for the northeastern Delaware Basin. Tzz inversion results provide detailed density distribution than conventional gravity inversion. Faults are expressed as steep gradients on Tzz map. Low-density source body edges, defined from Txz and Txy calculated anomalies, correlate with low-density areas are inferred to be hypogenic karst features in the central and southwestern study area. In Chapter 4, I define three domains of the rifted, continental crust in the Sergipe-Alagoas basin based on 2D seismic interpretations and 2D and 3D gravity models: 1) necked zone of continental crust; 2) hyper-extended zone of continental crust, and 3) the outer domain. The conjugate margin in northern Gabon, west Africa is wider with greater stretching and is explained by Precambrian basement fabrics that were oriented in a near-orthogonal to continental rifting. In Chapter 5, I used 2D seismic and well logs to define four megasequences bounded by regional unconformities: 1) pre-rift crystalline Precambrian basement, 2) syn-rift clastic sequence, 3) post-rift, sag sequence, and 4) passive margin sequence. Basin modeling shows mature Albian-Turonian source rocks overlain by Upper Cretaceous-Eocene reservoirs in the southwestern, indicating deepwater potentials. The northeastern area of the basin exhibits thin or absent source rocks due to magmatic activity and uplift during the Aptian.



Structural interpretation, Gravity model, Thermal maturity


Portions of this document appear in: Zhang, H., Mann, P., Bird, D.E., and Rudolph, K., 2021. Integration of regional gravity modeling, subsidence analysis, and source rock maturity data to understand the tectonic and hydrocarbon evolution of the Permian Basin, West Texas. Interpretation, 9(1), 161-181.